1. Field of the Invention
The present invention relates to a cargo container for an aircraft (i.e., an air cargo container), ships, freight trains or the like.
2. Description of the Relevant Art
Among various means of transport, the gross weight of an airplane is a substantial factor, and because even a slight reduction in weight is significant, FRP (i.e., fiber reinforced plastics) are now being used in many portions of an airplane.
Containers for an aircraft are absolutely necessary for carrying cargoes and passengers' baggages. A single airplane (particularly, an airplane used in an international flight), for example, is loaded with numerous containers. A freight plane, for example, can accommodate more than 100 containers. Consequently, the reduction in weight of the containers is effectively economical.
One presently used standard container of about 2 meters in width, about 1.5 meters in depth, and about 1.6 meters in height weighs about 90 kg. It has been said that if the weight of an airplane, used in, e.g., an international flight, can be reduced by 1 kg, the operation cost can be reduced by approximately 100 dollars per year. Despite such knowledge, little has been achieved in terms of reducing the weight of aircraft cargo containers.
The presently used containers are made of aluminum alloy. They are roughly handled when loaded into or unloaded from aircrafts; and many problems occur with such aluminum alloy containers (such as, forks of forklifts being able to pierce such containers, sustaining damage when colliding with each other or with cargoes contained therein, and requiring frequent repairs). Furthermore, with the recent increase of products being directly transported from places of production to consumers, the demand for heat insulated transport has thus increased. However, because aluminum alloy is high in heat conductivity, a heat insulating material must be used in large quantity to enhance heat insulation capability. Furthermore, dew condensation occurs on the outer surface, which contributes to yet another problem in the use of such aluminum alloy containers.
On the other hand, most of the presently used containers have a structure in the form of a box assembled by riveting or welding aluminum alloy plates onto an aluminum alloy frame together with reinforcing materials (such as, gussets). The above-mentioned standard container is made by assembling more than 50 parts. Further, in assembling such standard containers, more than 500 rivets are used. Such containers are heavy and require enormous time and cost in manufacture and assembling.
Furthermore, the presently used containers must use frames with a material having a large section modulus in order to secure the entire strength and rigidity of such containers. However, such frames contribute in the inability of such containers to have reduced weights.
As a method for solving the above problems of the containers used for aircrafts, JP-A-94-48480, e.g., proposes a container for an aircraft which includes sandwiched plates with an FRP as the outer skin and a foam as the core, along with the use of joining flanges therearound so that the respectively adjacent sandwiched plates may be joined through the flanges to form a box structure. Because this container uses an FRP and does not require a large frame, it is lighter in weight than the conventional aluminum alloy containers. However, because such containers do not use frames, the sandwiched plates used therein must be thick; as such, the intended beneficial effects are reduced. Furthermore, because of the joining structures in such containers, the manufacture and assembling thereof require a significant of time, effort and cost.
A need was therefore felt to provide a cargo container which avoids the above-discussed problems inherent in conventional containers.
It is therefore an object of the present invention to provide a container which is not only lighter in weight and higher in strength, but also excellent in heat insulation capability.
It is another object of the present invention to provide a container which is ideal for use, especially, in an aircraft, lighter in weight, and sufficiently strong and rigid.
It is another object of the present invention to provide a container which is also ideal for use in ships, freight trains or the like.
It is still another object of the present invention to provide a container which can be manufactured and assembled efficiently at far less time and cost.